Process for conducting heterogeneous chemical reactions

ABSTRACT

There is provided a new process for conducting heterogeneous chemical reactions in which a particulate catalyst is slurried in one of the reactant streams and fed into a distillation column reactor in a distillation reaction zone. The distillation reaction zone contains inert packing which provides the distillation structure for separation. The slurried catalyst trickles downward through the inert packing and is removed with the bottoms and separated therefrom for regeneration or replacement.

This application is a continuation in part of our earlier patentapplication Ser. No. 07/321,359 filed on Mar. 10, 1989 now U.S. Pat. No.5,019,669.

BACKGROUND OF THE INVENTION Field of The Invention

Broadly, the present invention relates to a method of conductingheterogeneous chemical reactions wherein the heterogeneous catalyst isslurried in one of the reactants and passed through a reactiondistillation zone containing inert distillation packing. The particulatecatalyst passes downward through the inert packing and is removed withthe bottoms product from which it is separated for replacement orregeneration

One species of the present invention relates to a process for thealkylation of organic aromatic compounds. More particularly theinvention relates to a process for the concurrent alkylation anddistillation of reaction components (reactants and products) in acatalyst bed wherein the catalyst is slurried in the organic aromaticcompound and passed through a reaction distillation zone to contactolefin feed. The reaction distillation zone comprises inert distillationpacking contained within the lower portion of a distillation columnreactor.

Related Art

Ethyl benzene and cumene are currently produced by the reaction ofbenzene and the respective olefin, i.e., ethylene and propylene by acidcatalysis. In some known processes the catalyst is highly corrosive andhas a relatively short life, e.g., AlCl₃, H₃ PO₄ on clay, BF₃ onalumina, and others require periodic regeneration, e.g., molecularsieves. The exothermicity of the reaction and the tendency to producepolysubstituted benzene require low benzene conversions per pass withlarge volume recycle in conventional processes.

U.S. Pat. Nos. 4,371,714 and 4,469,908 disclose straight pass alkylationof aromatic compounds using molecular sieve catalysts in fixed beds,however, both references disclose coking of the catalyst as a problemwhich necessitates frequent unit shut down and regeneration of thecatalyst. U.S. Pat. Nos. 4,316,997 and 4,423,254 both disclose the useof acidic resins in fixed beds for the alkylation of aromatic compounds.Coking is also a problem with these catalysts.

Recently a new method of carrying out catalytic reactions has beendeveloped, wherein the components of the reaction system areconcurrently separable by distillation, using the catalyst structures asthe distillation structures. Such systems are described variously inU.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,250,052; 4,302,356;4,307,254; and 4,443,559 commonly assigned herewith. Briefly, astructure described there is a cloth belt with a plurality of pocketsspaced along the belt, which is then wound in a helix about a spacingmaterial such as stainless steel knitted mesh. These units are thendisposed in the distillation column reactor.

In commonly owned, copending U.S. patent application Ser. No. 122,485filed 11/15/87, the process of alkylating aromatic compounds witholefins was carried out in a catalytic distillation system using acatalyst structure as described above, using either molecular sieves oracidic resins as particle packing in the pockets. This process has a fargreater resistance to coking than the straight pass systems.

The present system differs from catalytic distillation, because thecatalyst bed is not fixed and does not serve as the distillationstructure in the system. Hence the present system is designated asReactive Distillation™.

Advantages of the present invention are that the catalysts are nothighly corrosive and do not require periodic cyclic regeneration, theheat of reaction is used efficiently, only low volume of recycle isrequired and the feed ratios can approach unity.

SUMMARY OF THE INVENTION

Broadly the present invention is a method of conducting heterogeneouschemical reactions comprising the steps of:

(a) slurrying a solid particulate catalyst;

(b) concurrently:

(i) feeding said slurried catalyst to a distillation column reactor in areaction-distillation zone, said zone containing inert distillationpacking, said slurried catalyst moving downward through said inertpacking

(ii) contacting a first reactant with second reactant in the presence ofsaid slurried catalyst to react said first reactant with said secondreactant to form a reaction product; and

(iii) fractionating the resultant reaction product and the unreactedfirst reactant and second reactant in said distillation column reactor;and

(c) withdrawing said reaction product and said particulate catalyst fromsaid distillation column reactor at a point below said reaction zone.

In one embodiment the present invention is a process for the alkylationof organic aromatic compounds by contacting the organic aromaticcompound and a C₂ to C₂₀ olefin in a distillation column reactorcontaining a moving bed of acidic catalyst slurried in the organicaromatic compound feed in a distillation reaction zone containing aninert distillation packing thereby catalytically reacting said organicaromatic compound and said olefin to produce an alkylated organicaromatic product and concurrently in said moving bed fractionating theresultant alkylated organic product from the unreacted materials. Thedownwardly flowing catalyst slurry provides the catalytic sites whilethe inert packing provides the distillation sites. The alkylated organicaromatic product along with a portion of the unreacted organic aromaticcompound containing the slurried catalyst is withdrawn from thedistillation column reactor at a point below the fixed bed andadditional unreacted organic aromatic compound and unreacted olefin maybe taken off as an overhead. The catalyst is separated from the bulk ofthe liquid and a portion carried back to the reaction zone as a slurry.Another portion of the recovered catalyst is withdrawn and sent to aseparate regeneration. Regenerated catalyst may be returned to thereactor with the organic aromatic feed. Make up catalyst may also beadded to the aromatic feed or the catalyst recycle. The combinealkylation product and unreacted organic aromatic compound is separatedin a fractional distillation column, with the organic aromatic beingrecycled back to the reaction zone.

Suitable acidic catalysts include molecular sieves (mole sieves) andcation exchange resins. More specifically the mole sieve or cationexchange resin catalyst is of such a nature as to allow vapor flowthrough the bed to agitate and distribute the catalyst within the inertpacking, yet provide a sufficient surface area for catalytic contact asdescribed in the previously noted U.S. Pat. Nos. 4,215,011, 4,302,356and 4,443,559 which are incorporated herein in their entirety.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a schematic representation of a preferred embodiment ofone species of the present invention for producing ethyl benzene.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The exact location of the olefin feed will depend on the particularfeeds and the desired product. In one embodiment the olefin feed invapor phase to the reaction is preferably made below the catalyst bedthereby allowing mixing of reactants and agitation of the catalyst bed.In another embodiment the olefin feed to the reaction is preferably madeinto upper end of the fractionation column used to separate theunreacted organic aromatic compound form the alkylation product therebyallowing vaporization of this reactant along with the organic aromaticcompound and insuring good mixing to thereby react as much of the two aspossible and reduce or eliminate the olefin leaving the reactor asoverhead. A combination of olefin feed points may be employed.

The organic aromatic compound feed may be added at any point in thereactor, however, preferably it is added at the top of the distillationreaction zone. In any event a portion of the aromatic feed, sufficientto slurry the catalysts particles will be fed at the point where it isdesired to have the catalyst present in the reactor. The entire sectionof distillation structure need not have catalyst in it, in fact it iscontemplated that a substantial portion of the distillation reactor willcontain conventional distillation structures, such as, trays or platesabsent any added catalyst (other than incidental particles of catalystcarried up into that section by the boil up in the column. Also, inorder to achieve high selectivity toward monosubstitution (which is apreferred aspect of the present invention), there is a large excess ofthe organic aromatic compound to the olefin in the reactor in the rangeof 2 to 100 moles of organic aromatic compounds per mole of olefin, thatis the net molar feed ratio of aromatic organic compound olefin may beclose to 1:1, although the system is operated so as to maintain asubstantial molar excess of organic aromatic compound to olefin in thereaction zone. The alkylated product is the highest boiling material andis separated in the lower portion of the column usually as bottoms. Theorganic aromatic compound can be the second highest boiling or thirdhighest boiling component (excluding inerts) as noted above, however, byoperating with a large excess of the organic aromatic compound, themajor portion of the olefin is reacted; thereby reducing the separationand recovery problems. The operation of Reactive Distillation™ lies inan understanding of the principles associated with distillation. First,because the reaction is occurring concurrently with distillation, theinitial reaction product is removed from the reaction zone as quickly asit is formed. The removal of the alkylation product minimizespolysubstitution, decomposition of the alkylation product and/oroligomerization of the olefin. Second, because the organic aromaticcompound is boiling, the temperature of the reaction is controlled bythe boiling point of that component at the system pressure. The heat ofthe reaction simply creates more boil up, but no increase intemperature. Third, the reaction has an increased driving force becausethe reaction products have been removed and cannot contribute to areverse reaction (Le Chatelier's Principle).

As a result, a great deal of control over the rate of reaction anddistribution of products can be achieved by regulating the systempressure. Also, adjusting the through-put (residence time a liquidhourly space velocity ) gives further control of product distributionand degree of olefin conversion.

The temperature in the reactor is determined by the boiling point of theliquid mixture present at any given pressure. The temperature in thelower portions of the column will reflect the constitution of thematerial in that part of the column, which will be higher than theoverhead; that is, at constant pressure a change in the temperature ofthe system indicates a change in the reactant/product composition in thecolumn. To change the temperature the pressure is changed. Temperaturecontrol in the reaction zone is thus controlled by the pressure; byincreasing the pressure, the temperature in the system is increased, andvice versa. It can also be appreciated that in Reactive Distillation™ asin any distillation there is both a liquid phase (internal reflux) and avapor phase. Thus, the reactants are partially in liquid phase whichallows for a more dense concentration of molecules for reaction,whereas, the concurrent fractionation separates product and unreactedmaterials, providing the benefits of a liquid phase system (and a vaporphase system) while avoiding the detriment of having all of thecomponents of the reaction system continually in contact with thecatalyst which would limit the conversion to the equilibrium of thereaction system components.

The olefins may be C₂ to C₂₀ olefins, preferably C₂ to C₁₂ olefins,including normal and branched forms thereof. For example, suitableolefins are ethylene, propylene, butylene, isobutylene, 1-pentene,1-hexene, 2-hexene, 2, 3-dimethyl-1-pentene, 1-octene, diisobutylene,1-nonene and 1-decene, dodecene and the like. The olefins may containsubstituents which do not interfere with the alkylation. In onepreferred embodiment the olefin is a C₂ to C₄ olefin.

In some reactions according to the present invention, the olefin will bea higher boiling material than the organic aromatic compound, e.g., C₈to C₂₀ olefins. In such instances any unreacted olefin will appear inthe bottoms alkylation product, although a side draw may be used toreduce such material in the product to an insignificant level. However,operating the reaction with far less than a stoichiometric amount ofolefin in the reaction zone, as described, will normally keep theolefin. level in the bottoms low or entirely eliminated.

In those instances wherein the olefin is lower boiling than the organicaromatic compound, e.g., C₂ to C₇ compound there may be some olefingoing overhead even with the large molar excess present in the reactionzone. In those instances the overhead may be condensed to remove a majorportion of the organic aromatic compound and the olefin and inertsremoved for further separation or use. Similarly inerts such as thealkane of the particular olefin(s) which are often found in olefinstreams will be a possible contaminant, depending on its boiling point,in either the bottoms or overhead.

The organic aromatic compounds are preferably those having a boilingpoint of 250° C. or less under the pressure conditions of thedistillation column reactor. The organic aromatic compounds includehydrocarbons of one or more rings and 6 to 20 carbon atoms which maycontain substituents which do not interfere with the alkylationincluding halogen (Cl, Br, F and I), OH and alkyl, cycloalkyl, aralkyland alkaryl radicals of 1 to 10 carbon atoms. Suitable organic aromaticcompounds include benzene, xylene, toluene, phenol, cresol, ethylbenzene, diethyl benzene, naphthalene, indene, phenyl bromide,1-bromo-2-chloro-benzene, 1-bromo-4-oyolohexyl benzene,2-bromo-1,4-dihydroxy-benzene, 1(bromo-methyl) naphthalene,1,2-dihydronaphthalene and the like, a preferred group of compounds foruse in the present process is benzene, xylene, toluene, phenol, andcresol.

The mole ratio of organic aromatic compound to olefin in the reactionzone may be in the range of 2 to 100 : 1, preferably 2 to 50 : 1 andmore desirably about 2 to 10 : 1. The greater the excess of organicaromatic compound the more the selectivity to the monosubstitutedproduct is improved. Alkylation is forced to completion, since thesimultaneous and concurrent fractionation and removal of the alkylationproduct from the distillation column reactor does not allow the productsto contribute to the reverse reaction (Le Chatelier's Principle).However, very large molar excesses of organic aromatic compounds requirea very high reflux ratio, and a low unit productivity. Hence, thecorrect ratio of organic aromatic compound to olefin must be determinedfor each combination of reactants as well as the acceptable olefincontent in either the overhead or alkylation product (as describedabove), in a particular embodiment which is of current commercialimportance ethylene or propylene is reacted with benzene according tothe present invention to form ethyl benzene or cumene, respectively. Inboth of these reactions the olefin is the most volatile component and itis desirable to react it rather than have some carried off overhead.

The length of the catalyst bed that portion of the distillation reactorwhere the down flowing catalyst slurry is present), particularly thatportion wherein the reactants are in contact and the major portion ofthe reaction occurs, depends on the reactants, location of the olefinfeed and the acceptable unreacted olefin in the streams leaving thetower. Some degree of development testing will be required for each setof reactants and parameters of stream purity following presentdisclosures.

The present alkylation reaction can be carried out at sub-through superatmospheric pressure, e.g., 0.20 to 40 atmospheres. The temperature willvary depending on the reactants and product. Furthermore, thetemperature along the column will be as in any distillation column, thehighest temperature will be in the bottom and the temperature along thecolumn will be the boiling point of the compositions at that point inthe column under the particular conditions of pressure. Moreover, theexothermic heat of reaction does not change the temperature in thecolumn, but merely causes more boil up. However, the temperatures withinthe column with the above considerations in mind will generally be inthe range of 50° C. to 500° C., preferably 70° C. to 500° C. for themole sieve and 70° C. to 200° C. for the cation exchange resin, and morepreferably in the range of about 80° C. to 300° C. at pressures of 0.5to 20 atmospheres for the mole sieve, and about 80° C. to 150° C. at0.25 to 15 atmospheres for the resin catalyst.

Molecular sieves are porous crystalline, three-dimensionalalumina-silicates of the zeolite mineral group. The crystal skeleton iscomposed of silicon and aluminum atoms each surrounded by four oxygenatoms to form. The term molecular sieve can be applied to both naturallyoccurring zeolites and synthetic zeolites. Naturally occurring zeoliteshave irregular pore size and are not generally considered as equivalentto synthetic zeolites. In the present invention, however, naturallyoccurring zeolites are acceptable so long as they are substantiallypure. The balance of the present discussion shall be directed to thesynthetic zeolites with the understanding that natural zeolites areconsidered equivalent thereto as indicated above, i.e. in so far as thenatural zeolites are the functional equivalents to the syntheticzeolites.

Usually synthetic zeolites are prepared in the sodium form, that is,with a sodium cation in close proximity to each aluminum tetrahedron andbalancing its charge. To date seven principal types of molecular sieveshave been reported, A, X, Y, L, erionite, omega and mordenite. The Atype have relative small pore size. By the term pore size is meant theeffective pore size (diameter) rather than the free pore size(diameter). Types X and Y have larger pore size (approximately 10 Å) anddiffer as to the range of ratio of Al₂ O₃ to SiO₂ as:

Type X--------------- Al₂ O₃ /2.0-3.0 SiO₂

Type Y--------------- Al₂ O₃ /3.0-6.0 SiO₂

Type L and the other types listed have still higher ratios of SiO₂ toAl₂ O₃

The mole sieve catalysts employed in the present invention are the acidform mole sieves or exhibit acidic characteristics. The acid form of themole sieves is commercially available, but also may be prepared bytreating the mole sieves with acid to exchange Na for hydrogen. Anothermethod to produce the acid form is to treat the mole sieve withdecomposable cations (generally ammonium ions) to replace Na with thedecomposable ions and thereafter to heat the mole sieve to decompose thecation leaving the acid form. Generally the Na form mole sieve istreated with ammonium hydroxide to remove the Na and thereafter the molesieve is heated to a temperature of about 350° C. to remove the ammonia.The removal of Na⁺ ions with NH₄ ⁺ is more easily carried out than withmultivalent ions as described below and these catalysts are generallymore active, but less stable to heat than the multivalent cationexchange forms. Mole sieves, which have had their alkali metal reducedto low levels by partial treatment with NH₄ ⁺ and partial multivalentmetal cation exchange, possess increased activity and increasedstability. In addition to mole sieves which are acidic according to theBronsted Theory those mole sieves which exhibit acidic characteristicsunder the Lewis Theory, for example, calcium exchanged mole sieves aresuitable for the present reaction. By exchanging the univalent cations(e.g.) Na⁺) with multivalent cation, strong ionic activity is imparted.The ratio of SiO₂ : Al₂ O₃, valence and radius of the cation and theextent of exchange all affect the catalyst activity. In general activityincreases with (1) increased SiO₂ Al₂ O₃ ratio, (2) decreased cationradius and an increase in cation valence. The effect of replacingunivalent ions (e.g. Na⁺ ) with bivalent (e.g. Ca⁺⁺) is much greaterthan replacing the bivalent ions with cations of greater valence.

The various types of mole sieves having reduced alkali metal content arecharacterized as the acid form molecular sieve and are all contemplatedas useful in the present invention.

It would appear that the pore size within the crystal lattice may affectthe selectivity. According to one theory of molecular sieve catalyticactivity, zeolite catalysis occurs primarily inside the uniform crystalcavities, consequently zeolitic catalyst activity depends on the numberof aluminum atoms in the crystal and thus on the chemical composition ofthe crystal. Moreover, these catalytic sites are fixed within the rigidstructure of the crystal, so that access to site can be altered byaltering the structure of the crystal.

The acid form mole sieves are generally produced and available asparticles in the range of <10 micron (powders) to 0.2 inch in diameter(beads).

In this form the mole sieves form too compact a bed and will notfunction adequately in a distillation, since there is a very largepressure drop through the bed and the free flow of internal reflux andrising vapor is impeded. However, when slurried with the aromatic andfed to a fixed bed of inert distillation packing and further agitated bya vapor (e.g., olefin) rising through the bed, they present only anincremental increase in the hydrostatic resistance in the tower to theflow of the vapors, than the Carrier liquid (e.g., aromatic feed) alone.

Suitable acid cation exchange resins include those which containsulfonic acid groups, and which may be obtained by polymerization orcopolymerization of aromatic vinyl compounds followed by sulfonation.Examples of aromatic vinyl compounds suitable for preparing polymers orcopolymers are: styrene, vinyl toluene, vinyl naphthalene, vinyl ethylbenzene, methyl styrene, vinyl chlorobenzene and vinyl xylene. A largevariety of methods may be used for preparing these polymers; forexample, polymerization alone or in admixture with other monovinylcompounds, or by crosslinking with polyvinyl compounds; for example,with divinyl benzene, divinyl toluene, divinylphenylether and others.The polymers may be prepared in the presence or absence of solvents ordispersing agents, and various polymerization initiators may be used,e.g., inorganic or organic peroxides, persulfates, etc.

The sulfonic acid group may be introduced into these vinyl aromaticpolymers by various known methods; for example, by sulfating thepolymers with concentrated sulfuric and chlorosulfonic acid, or bycopolymerizing aromatic compounds which contain sulfonic acid groups(see e.g., U.S. Pat. No. 2,366,007). Further sulfonic acid groups may beintroduced into the polymer which already contain sulfonic acid groups;for example, by treatment with fuming sulfuric acid, i.e., sulfuric acidwhich contains sulfur trioxide. The treatment with fuming sulfuric acidis preferably carried out at 0° to 150° C. and the sulfuric acid shouldcontain sufficient sulfur trioxide so that it still contains 10 to 50%free sulfur trioxide after the reaction. The resulting productspreferably contain an average of 1.3 to 1.8 sulfonic acid groups peraromatic nucleus. Particularly, suitable polymers which contain sulfonicacid groups are copolymers of aromatic monovinyl compounds with aromaticpolyvinyl compounds, particularly, divinyl compounds, in which thepolyvinyl benzene content is preferably 1 to 20% by weight of thecopolymer (see, for example, German Patent Specification 908,240). Theion exchange resin is generally used in a granular size of about 0.25 to1 mm, although particles from 0.15 mm up to about 2 mm may be employed.The finer catalysts provide high surface area, but could also result inhigh pressure drops through the reactor requiring higher vaporvelocities to agitate the catalyst. The macroreticular form of thesecatalysts have much larger surface area exposed and limited swellingwhich all of these resins undergo in a non-aqueous hydrocarbon mediumcompared to the gelular catalysts.

The concentration of catalyst in the slurry can vary over a wide range,depending on such process variables as the catalyst particle size,particle density, surface area, olefin feed rate, ratio of aromatic toolefin, temperature and catalyst activity. As an illustration, a Y typemole sieve, 80-20 mesh particle size, 770 m² /gm. surface area, in thereaction of ethylene with benzene with benzene being fed at 78 g/min,ethylene at 28 g/min, benzene reflux ratio of 4:1, the concentration ofcatalyst in the benzene feed plus recycle could be in the range of 50 to100 grams per liter. The competing considerations of reactivity andphysical dynamics of the reactants in a particular system maynecessitate adjustment of several variables to approach a desiredresult.

The drawing illustrates one species of the present invention, i.e., theproduction of ethyl benzene by alkylating benzene with ethylene and apreferred embodiment of that species. Referring to the drawing thedistillation column reactor is divided into two sections. The uppersection 1, which may be a separate column is either completely filledwith inert distillation packing or at least has the lower one-third toone-half filled with such packing as at 101. The upper two-thirds toone-half of the first section 1 may alternatively have conventionaldistillation trays 102. The lower portion 101 of the first section isconsidered the reaction zone for reasons which will become apparent. Thesecond section 2, below the first may conveniently be a secondconventional distillation column having conventional trays 201.

The particulate catalyst as described is slurried into the organicaromatic feed and the two combined are fed to the top of the reactionzone 101. The olefin is vaporized, as in the upper end of the secondsection 2 as shown, and fed to the lower end of the reaction zone 101.The vaporous olefin rises in the reaction zone agitating the slurriedcatalyst and insuring good contact. As the olefin rises through theslurry bed it is in contact with the organic aromatic and catalyst thusreacting the two to form an alkylation product. In the embodiment shown,ethylene or propylene (propylene) reacts with benzene to form ethylbenzene or cumene. A molar excess of benzene to olefin is maintained inthe reaction zone such that essentially all of the olefin is consumed.Unreacted benzene is boiled out of the catalyst mixture up into theconventional distillation trays 102 where an alkylation product isseparated back down to the distillation reaction section and out thebottom of the reaction zone 101. The slurried catalyst along with someof the unreacted benzene is also carried out the bottom since separationis not complete. The bulk of the liquid (unreacted benzene andalkylation product) is separated from the catalyst in a separator 3 andfed to the top of the second section 2 where separation is completed.The catalyst, still slurried in some of the liquid is returned to thereaction zone. Some of the catalyst may be removed in a slip stream forregeneration and reslurrying with benzene feed.

In the second section the separation of benzene and alkylation productis complete with benzene being returned to the reaction zone. As noteabove, the olefin may be fed to the top of the second section 2 to bevaporized prior to introduction to the reaction zone 101. Alkylationproduct is withdrawn from the bottom of second section 2 where some isheated in reboiler 202 to provide heat for the distillation.

Benzene is taken overhead the first section 1 where it may be condensedin condenser 103 and collected in receiver/separator 104. Substantiallyall of the benzene is returned to the distillation column reactorsection 1 as reflux and to aid in the control of the molar ratio ofbenzene to olefin in the reaction zone. Any unreacted or inert gases areremoved in the separator/receiver 104 for further processing as desired.The recycle of slurried catalyst in benzene-alkylation product from thebottom of the reaction zone may also be used to control the molar ratio.

While the specific reaction of olefins and organic aromatic compounds inthe presence of a suitable particulate acidic catalyst is illustrated,it is to be expected that for any particular feed streams and selectivereaction therein, the specific conditions of reaction will need to bedetermined by some minimum amount of experimentation employing theinvention described herein and using information provided herein to theconduct the process in accordance with the present invention. Thecatalytic material may be any material appropriate for the reaction athand, that is, it may be an acid catalyst (as illustrated) or a basiccatalyst or others such as catalytic metals and their oxides or halidessuitable for a multitude of catalytic reactions and of course,heterogeneous with the reactants or other fluids in the system. Forexample, the reaction of C₄ and/or C₅ isoolefins, such as isobutene withC₁ -C₆ alcohol such as methanol or ethanol to produce the correspondingether by contacting the alcohol and the appropriate olefin in thepresence of a downwardly descending slurry of the above described acidcation exchange resin.

The invention claimed is:
 1. A method for conducting heterogeneouschemical reactions comprising the steps of:(a) slurrying a solidparticulate catalyst in a first liquid reactant stream; (b)concurrently:(i) feeding said first liquid reactant stream containingsaid slurried catalyst to a distillation column reactor in areaction-distillation zone, said zone containing inert distillationpacking, said slurried catalyst moving downward through said inertpacking; (ii) contacting said first reactant with a second reactant inthe presence of said slurried catalyst to react said first reactant withsaid second reactant to form a reaction product; and (iii) fractionatingthe resultant reaction product and the unreacted first reactant andsecond reactant in said distillation column reactor; and (c) withdrawingsaid reaction product and said particulate catalyst from saiddistillation column reactor at a point below said reaction zone.
 2. Themethod according to claim 1 further comprising the steps of:(d)separating said catalyst from said reaction product; and (e) returningsaid separated catalyst to said first liquid reactant stream to beslurried therein.
 3. The method according to claim 2 further comprisingthe step of removing a portion of said separated catalyst forregeneration prior to returning said portion to said first liquidreactant stream to be slurried therein.
 4. The method of claim 1 whereinsaid first reactant comprises a C₁ -C₆ alcohol and the second reactantcomprises C₄ or C₅ isoolefins.
 5. The method of claim 5 wherein saidalcohol comprises methanol.
 6. The method of claim 5 wherein saidalcohol comprises ethanol.
 7. The method of claim 5 wherein said secondreactant comprises C₄ isoolefin.
 8. The method of claim 5 wherein saidsecond reactant comprises C₅ isoolefin.
 9. The method of claim 6 whereinsaid second reactant comprises C₄ isoolefin.
 10. The method of claim 6wherein said second reactant comprises C₅ isoolefin.
 11. A method forconducting heterogeneous chemical reactions comprising the steps of:(a)slurrying a solid particulate catalyst in a first reactant stream; (b)concurrently(i) feeding said slurried catalyst and said first reactantstream to a distillation column reactor in a reaction-distillation zone,said zone containing inert distillation packing, said slurried catalystmoving downward through said inert packing; (ii) feeding a secondreactant stream to said reaction-distillation zone thereby contactingsaid second reactant with said first reactant in the presence of saidslurried catalyst to react said first reactant with said second reactantto form a reaction product; and (iii) fractionating the resultantreaction product and the unreacted first reactant and second reactant insaid distillation column reactor; and (c) withdrawing said reactionproduct and said particulate catalyst from said distillation columnreactor at a point below said reaction zone.
 12. A method for conductingheterogeneous chemical reactions comprising the steps of:(a) slurrying asolid particulate catalyst in a first reactant stream; (b)concurrently(i) feeding said slurried catalyst and said first reactantstream to a distillation column reactor in a reaction-distillation zone,said zone containing inert distillation packing, said slurried catalystmoving downward through said inert packing; (ii) feeding a secondreactant stream to said reaction-distillation zone thereby contactingsaid second reactant with said first reactant in the presence of saidslurried catalyst to react said first reactant with said second reactantto form a reaction product; and (iii) fractionating the resultantreaction product and the unreacted first reactant and second reactant insaid distillation column reactor; (c) withdrawing said reaction productand said particulate catalyst from said distillation column reactor at apoint below said reaction zone; (d) separating said catalyst from saidreaction product; (e) removing a portion of said separated catalyst forregeneration; (f) regenerating said removed portion of said separatedcatalyst; and (g) combining the remainder of said separated catalyst andsaid regenerated portion of said separated catalyst; and (h) returningsaid combined separated catalyst to said first stream to be slurriedtherein.
 13. The method of claim 12 wherein said second reactant streamis lower boiling than said first reactant stream and said secondreactant stream is fed as a vapor below said reaction-distillation zoneto agitate said slurried catalyst in said reaction zone.